Alkylation of aromatic hydrocarbons



E. F. BULLARD ETAL' ALKYLATION OF AROMATIC HYDROCARBONS Filed Nov. 2,1942 0') invenors'. Edwin F. Bullard g John Anderson I Sumner H.McAlls'fzr bg *heir* AHorneg// i fg,

Patented Aug. 13, 1946 UNITE STATES r vorricle ALKYLATION oFArtor/nrrl'e` HYDRocARBoNs l e Delaware Application November 2, 1942,Serial No. 464,286 l -This invention relates to the reaction of aromatichydrocarbons with alkylating agents and particularly to the productionof motor fuels and motor fuel components by alkyl-ation of suchhydrocarbons. It deals with an improved method for carrying out suchalkylations whereby products having superior characteristics may beobtained.

An important object of the invention is to provide a more efcient andeconomical method of alkylating aromatic hydrocarbons in the vaporphase. Another object is to improve vapor phase methods of reactingbenzene and the like in the presence of solid acid alkylation catalysts.A further object is to increase the yield of desirable alkylationproducts by reacting aromatic hydrocarbons with oleiins. Still anotherobject is to produce aromatic alkylation products having superiorproperties, particularly as regards their motor fuel characteristics.Other objects and advantages of the process of the invention will beapparent from the following description.

Various methods of alkylating benzene and higher aromatic hydrocarbonshave been proposed from time to time, but they have not been successfulbecause of their inefficient conversion of the starting materials and/ortheir poor quality of products. It has now been found that thesedisadvantages of prior alkylation methods may be overcome by the use ofan improved reaction system employing, preferably, more advantageousreaction conditions.

The new process may be applied to the alkylation of a wide variety ofaromatic hydrocarbons, although when used for the production of motorfuels or motor fuel components volatility considerations make it moreadvantageous to use lower boiling aromatic hydrocarbons, particularlybenzene and toluene. Where such considerations are of lesser importance,higher boiling compounds may be employed. ThusJ ethyl benzene, thexylenes, propyl or isopropyl benzene, mesitylene,the butyl benzenes, thecymenes, and homologues, naphthalene and its corresponding substitutionproducts, and the like may be used. The source of the aromatic startingmaterial is -not important. The coal tar industry provides la convenientsource of benzene, toluene, etc., but petroleum fractions containingthese compounds, particularly the highly aromatic fractions obtainableby catalytic reforming or hydroforming, are also useful. Such fractionsmay advantageously be subjected to extraction with suitable solvents,for example, as described in U. S. Patent 2,114,524, to increase theconcentration of the aromatic 11 Claims. (Cl. 26d-671) hydrocarbon to bealkylated before they are used in the process.

Alkylating agents Whichpmay be used in the process include olens,particularly suitable fractions of petroleum crackingvproductscontaining ethylene, prop ylena isobutylene, normal butylenes, theamylenesor mixtures of one o1' more such olefms.',1nstead of the olens,polymers thereof'mayg-be used, Not only may ethers, alcohols and esterscorresponding to the foregoing olens beemployed, but also ctherethers,alcohols and esters, such as dimethyl, methyl-ethyl,

methyl-isopropyl, di-normal propyl, ethyl-isopropyl and like ethers,methyl and higher primary alcohols, may be used. Either inorganic ororganic esters such as halides, ksulfates, phosphates, borates,formates, acetates and the like may be employed as alkylating agents.The alkylating agent-.may be used in a pure or substantiallypure formeras', mixtures of one or kmore ,alkylating agents with or without othermaterials which donot interfere with the desired reaction.v

As catalytsfor the process, acids are used. Most preferably the chosenacid catalyst is employed with a suitable carrier so that it mayconveniently be used in solid form as packing for tower or tube typereactors. Acids of phosphorus are particularly suitable for thispurpose, particularlymixtures of ortho or meta phosphoric acid orpyrophosphoric` acid with kieselguhr or other suitable clays or earthssuch as areV described in U..S. Patent 1,993,513. However, othercatalysts such as sulfuric acid, hydrogen fluoride or the like adsorbedon porous supports. or as a coating or lm on non-porous packing materialor the like may also be used in the process. It is also feasible to'employ liquid acid alkylation catalysts inthe process.

The alkylation is preferably carried out in the vapor phase with asubstantial excess of aromatic hydrocarbonsbased on the alkylating agentused. It has already been Suggested that in alkylating benzene 1anexcess be used to suppress formation of higher alkylation products. Suchexcess benzene is not sucient for most efficient reaction and it hasbeen found desirable to use at least three,l and more preferably ve toten or more, mols `of the aromatic -hydrocarbons being alkylated per molYof olen or equivalent alkylating agentV in the process of theinvention. In this way not onlylare undesirable side reactions such asthe formation of poly-alkylated products substantially eliminated, but.also high conversions 3 of the alkylating agent to valuable products areobtained.

The reaction is most advantageously carried out under superatmosphericpressure; preferably pressures of 200 toA 400 pounds per square inch areused. The temperature and time of contact which will be most desirablewill depend upon the particular catalyst used and the alkylating agentchosen. For the alkylation of benzene with oleiins such as propylene inthe presence of phosphoric acid, a temperature of about 200 C. to 400C., preferably about 250 C, to 300 C., and a hydrocarbon feed rate ofabout 0.1 to 0.8 gallon per hour per pound of catalyst are mostadvantageous. This combination of reaction conditions gives resultswhich are markedly superior with respect to yields, conversions andefficiency of operation to those obtained by other methods.

It has previously been considered that alkylation of aromatichydrocarbons accomplished a suicient purification -of the reactants andproducts so that no other treatment was" necessary. However, to obtainthe -best results according to thepresent invention, it is desirable totreat the feed stocks used, especially the aromatic hydrocarbon, forremoval of undesirable components, particularlysulfur-containingoompounds such as thiophen'e, since otherwise thesecompounds undergosimultaneous reaction and appear in the product,materially reducing its quali-ty especially for motor fuel use. Suchtreatment not only improves the quality of the product and-simplifiesits further processing, but also improves the effective life ofthecatalyst in the process.

For the treatment of benzene, for example, it is-preferredto usesulfuric acid of about 90% to 100% concentration' at a temperature ofabout 10 Clto. 60 C.,preferably about 98% concentration at about-C. Aratio of acid to benzene above 1 tolO by volume isdesirable 'and ratiosof about 0.16:1 to 025:1 are preferred. The acid and benzene may beintimately contacted by agitation in a mixer or other vessel,countercurrent now in a tower which may or may not contain packing topromote-'intimate mix-ing, or. in any other suitable manner. A contacttime of acid with. benzenegof at least 3Yminutes, and more preferably/ito -6 minutes or longer, is desirable. 'Contact in a pluralityofreactionstages is advantageous in reducingfthe amount of acid requiredfor treatment of a givenv volume of aromatic hydrocarbon. After thevacid treatment the aromatic hydrocarbon is Washed with a base such aslaqueous caustie soda before being used in the alkylation step of theinvention.

Merely treating the feed stocks before alkylation is not suicient toobtain the best results in the present process. It has been foundnecessary to return to the sulfuric acid treating stage at least a partof the excess unreacted aromatic hydrocarbon recovered from the product.Since this aromatic hydrocarbon has been previously subjected to thesulfuric acid treatment as well as to the alkylating conditions, itwould be thought that it would'be ideal material for recycling directlyto the alkylation and that further treatment could not possibly be ofadvantage. It was surprising therefore' to discover that by feeding apart of this stream to the sulfuric acid treating unit instead of to thealkylation reaction, materially improved results, especially withrespect to product quality, were obtained. The exact nature of allthechanges in the recycle benzene or other aromatic hydrocarbon which areresponsible for the improvedY resultsisV notknown but it has been founddesirable to submit at least one-tenth, and preferably at leastonefourth, of such aromatic hydrocarbon to treatment with sulfuric acidunder the previously describedconditions before returning it to thealkylation unit. The treatment may be effected along with or separatelyfrom the treatment of the initial feed.

The attached drawing shows, diagrammatically, an assemblage of apparatusparticularly adapted for producing cumene by reaction of benzene withpropylene according to the invention. In the drawing only the moreimportant pieces of equipment are indicated for the most part, since thelocation of auxiliary equipment such as pumps, valves, storage tanks,pressure-, temperatureand flow-regulating and measuring devices, heatexchangers, and the like will be evident to those skilled in the art. Inthe arrangement of the drawing, benzene from a source not shown,y is fedby line I to a mixer 2 in which it is contacted with sulfuric acidintroduced via line 3. The resulting mixture passes by line 4 to settler5 from which acid is taken olf by line 6 and returned to mixer 2 bylines l and 3. A part of the acid maybe continuously or intermittentlywithdrawn from the system by line 8. The partially treated benzene isconducted by line 9, together with fresh acid introduced by line I0, tomixer II where a further intimate mixing is effected. The resultingemulsion is taken by line I2 to settler I3 in which the acid andhydrocarbon phases are again separated. The separated acid is taken offbyline I4 and a part returned to the second reaction stage by line I5while the remainder is conducted to line 3 by line I6 to furnish thepartially spent acid for the first reaction stage. The thus-treatedhydrocarbon is fed by line I'I to mixer I8 which is supplied,continuously or intermittently,` with a caustic from line I9. Thecaustic-benzene mixture is fed via .line 20 to settler 2l from whichcaustic is withdrawn by line 22. The withdrawn caustic is returned tomixer I8 for further use by lines 23 and I'I, a part being withdrawn asnecessary by line 24. The treated benzene is taken off by line 25 andmixed with propylene or propylene-containing hydrocarbon which mayadvantageously have been caustic-treated in theY same manner as theacid-treated benzene introduced via lines 26 and 2l. Alternatively, thepropylene may be introduced via lines 26 and 29 and thus becaustictreated along with the benzene. In either case the mixture ofpropylene and treated benzene is conducted by line 29 to reactors30which are shown as a bank of tubes through which the reaction mixtureflows in parallel. The reactors contain Ygranules of phosphoric acid orother suitable acid catalyst not shown and are heated by steam or othermeans also not shown. They are preferably constructed to withstandpressures of the order of 1000 pounds per square inch. As previouslyindicated, however, other forms of reactors may be used and the reactionmixture may flow through two or more reactors in series instead ofthrough all reactors in parallel as shown. Line 40 is provided forintroducingl steam or other activating or controlling agent as may berequired to maintain the activity of the catalyst. l It may also be usedto introduce fresh-catalyst or catalyst-regenerating agents.v 1 f Thereacted hydrocarbon mixture, comprising cumene and ,unreacted' benzeneand propylene and any inert materials introduced-with the feed orotherwise, is withdrawn from the reactors by line 3| and conducted todepropanizer column 32 in which the lower boiling components areseparated and taken off overhead by line r3.3.l The remaining cumene andbenzene are taken'oi as bottoms by line 34 and fed to debenzeni'zercolumn 35 from which the unreacted benzene is removed by line 36 andreturned to the reaction by line 31 after withdrawal of a part of line38 for treatment with sulfuric acid in mixersl 2 and Il along with thefresh benzene feed. The cumene produced is recovered by line 39.

The following examples further illustrate the advantages ofthe process,although no limitation on the invention is to be inferred therefrom asthe same principles may be applied to the reaction of the same or otheraromatic hydrocarbons with other alkylating agents.

Example I Cumene in Propylene Mol ratio benzene to oleiin the productconverted p Per cent Per cent VEaxrmple AII The effect of pressure onthe reaction was determined in a series of tests using a solidphosphoric acid catalyst and a feed containing 5 mols of benzene per molof propylene. Y

6 Example IVk The effect of sulfuric acid treatment of the `benzene feedon the quality of the reaction products was shown by the followingcomparative runs made with coal tar benzene which was reacted withpropylene in the presence of solid phosphoric acid catalyst using areaction temperature of 200 C. to 250 C. and a pressure of 250 poundsper square inch. The benzene in one case was used directly and in theother case was treated with 25 poundsv of 98% sulfuric acid per barrelat about 20 C.. The molar ratio of benzene to olen in each .case was 5:1and the feed rate was 1800 to 2000 grams,n of ,hydrocarbon per liter ofcatalyst per hour.

Sulfuric acid- Untreated treated benzene benzene Sulfur in the benzene(wt. per cent) 0. 47 0.06 Oleins in the benzene (wt. per cent) 0. 76 0.09 Sulfur in the cumene (wt. per cent) 0. 51 0.05

The'propylene conversions and cumene yields for different periods ofcatalyst use were as follows:

The products were tested as 5% and 10% blends in 100 O. N. aviationgasoline with a nal tetraethyl lead content of 4.0 cc. per gallon.

Rating in 3-C engine test Product from untreated Product from sulfuricFeed rate benzene acid-treated benzene lgrmsof P 1 C y T0931- TOPY @nemene 5 blend Is -octane 0.7 co. f Is tan 1.1 fle d rssug bumper ggg.Pagar inthe teaming. tristi. a Sq h.1` Der non 111 ture sion Crude 10%blend Isooctane+l.l cc. of Iso-octane-l-L cc. of lead 'I Clisft the feedDTOdllCt n lead tetraethyl. tetractliyl.`

space) Copper dich gum (mg./100 ml.) Per cem) C'. Per cent Per cent2,030 r2 esta a as 2,0 0 2,000 8.2 20o-250 92 90 Product from 4,000 8.2200-250 s1 ss 55 untreated treated 4, 000 8.2 20o-250 s2 90 benzenebenzene 57 blend 5 1 Example HI 103]o blend 10 2 Effect of temperaturewas determined in comparative tests using a feed rate of 2000 grams ofhydrocarbon per hour per liter of catalyst space, a benzene to propylenemol ratio of 5 to 1, and a pressure of 250 pounds per square inch. Thepropylene concentration in the feed was 8%-8.2%

Cumene in Propylene Temperature the product converted Per cent yPer centl200 C 90 60 70 200-250 C 90 90 The catalyst life under these conditionswas of the order of gallons of cumene per pound of catalyst. At highertemperatures the life decreases.

Considering the small amount of cumene in these blends, the effect ofthe sulfuric acid treatment of the benzene is seen to be remarkable.

Example V aetaevfi We claim as our invention:

1. A process of producing cumene which comprises treating benzene withsulfuric acid of at least 90% concentration at about 10 C, to 60 C. fora time sufficient to reduce the thiophene content thereof, admixing thetreated benzene with propylene in the ratio of 3 to 10 mols of benzeneper mol of olen and contacting the mixture under a pressure of between250 and 600 pounds with a solid phosphoric acid catalyst at atemperature of 200 C. to 300 C. using a space Velocity of 0.1 to 0.6gallon of hydrocarbon per pound of catalyst per hour, fractionating theresulting products to separate unreacted benzene, and returning at least4a part of `the thus-recovered benzene to said sulfuric acid treatmentfor further reacton in the process.

2. A process of producing cumene which comprises passing a mixture ofbenzene and propylene in a molar ratio of at least 4 to 1 over a solidphosphoric acid catalyst at a temperature of 200 C. to 300 C. and apressure of at least 250 pounds per square inch, separating at least apart of the unreacted benzene from the products, contacting at least apart of said separated benzene with sulfuric acid of at least 90%concentration, and returning the acid-treated benzene for furtherreaction in the presence of said phosphoric acid catalyst.

3. A process of producing cumene which' comprises treating benzene withsulfuric acid of at least 90% concentration for a time suflicient toreduce the thiophene content thereof, reacting the acid-treated benzenewith propylene in the presence of a solid phosphoric acid catalyst undera pressure of at least 250 pounds using aV molar ratio of benzene topropylene of at least 4 to 1 and a temperature between 200 C. and 300C., and recovering the resulting cumene.

L1. A process of producing cumene which comprises contacting benzenewith between one-tenth and one-fourth of its volume of sulfuric acid of95% to 100% concentration for a period of 5 to 10 minutes at about o C.to 30 C. sufficient to materially reduce the thiophene content thereof,neutralizing the acid-treated benzene, and contacting a mixture of saidbenzene Vand an isopropyl-ating agent containing at least three timesthe stoichiometric amount of benzene to isopropylating agent with asolid acid alkylation catalyst under alkylation conditions.

5. A process of producing cumene which comprises contacting benzene withconcentrated sulfurie acid for a time sucient to substantially reducethe thiophene content thereof, and reacting a molar excess of theresulting benzene with an isopropylating agent in the presence of asolid acid alkylation catalyst under a pressure of 250 to600 pounds.

6. A processof producing cumene which comprises reacting a substantialmolar excess of benzene with an isopropylating agent under a pressure ofat least 250 pounds per square inch in the presence of a. solid acidalkylating catalyst, separating unreacted benzene from the reactionproducts and contacting the separated Vbenzene with concentratedsulfuric acid for a time sufci'ent'to substantially reduce the thiophenecontent thereof, and returning the sulfuric acidtreated benzene toreaction with further isopropylating agent.

7. A process of producing an alkyl benzene which comprises reacting asubstantial molar excess of benzene with an alkylating agent under apressure of at least 250 pounds per square inch in the presence of Iasolid acid alkylating catalyst, separating unreacted benzene from thereaction products and contacting the separated benzene with concentratedsulfuric acid for a time sufcient to substantially reduce the thiophenecontent thereof, and returning the sulfuric acidtreated benzene toreaction with further alkylating agent.

8. A process of producing an alkyl benzene which comprises contactingbenzene with concentrated sulfuric acid for a time suflicient tosubstantially reduce the thiophene content thereof, and reacting a molarexcess of the resulting benzene 'With an alkylating agent in thepresence of a solid acid alkylation catalyst under a pressure 0f '250 to600 pounds. Y

9. A process of alkylating an aromatic hydrocarbon which comprisestreating said hydrocarbon with at least one-tenth of its Volume ofconcentrated sulfuric acid for a time sufficient to materially reducethe thiophene content thereof, and reacting a molar excess of theresulting aromatic hydrocarbon with an alkylating agent under a pressureof at least 250 pounds per square inch in the presence of a solid acidalkylation catalyst under alkylation conditions. y 10. A process ofalkylating an aromatic hydrocarbon which comprises treating saidhydrocarboniwith sulfuric acid of at least concentration at 10 C. to 60C. for a time of at least 5 minutes sufiicient to materially reduce thethiophene content thereof, reacting a molar excess of the resultingaromatic hydrocarbon with an alkylating agent in the presence of a solidacid alkylation catalyst under alkylation conditions, separatingunalkylated aromatic hydrocarbon from the reaction products, andreturning at least a part thereof to said sulfuric acid treatment.

11. A process of alkylating an aromatic hydrocarbon which comprisesreacting a molar excess of said hydrocarbon with an alkylating agentunder a pressure of at least 250 pounds per square inch in the presenceof a solid acid alkylation catalyst under alkylation conditions,separating unalkylated aromatic hydrocarbon from the reaction productsand contacting at least a part thereof with sulfuric acid for a timesufficient to materially reduce the thiophene content thereofgandreturning the thus-treated hydrocarbon to the alkylation reaction.

EDWIN F. BULLARD. JOHN ANDERSON. SUMNER H. MCALLISTER.

